DESCRIPTION (from applicant's abstract): Auditory and vestibular response dynamics are crucial for successful processing of "real world" change, but are highly susceptible to disease processes of the ear. Consequently, neurotologic deficits that limit the processing of dynamic auditory and vestibular stimulation may be especially devastating. The goals of this K24 Award are to (1) establish the peripheral and central mechanisms in neurotologic disease that underlie dynamic processing deficits, (2) develop new diagnostic and teaching tools for characterizing these deficits, and (3) prepare young clinical investigators for careers in patient-oriented research to attack these and other important clinical research problems. Two classical clinical problems are addressed with experiments, models, and simulations in this research. The first problem focuses on vestibular ocular reflex (VOR) response deficits that arise from unilateral peripheral neural vestibular disease. Such deficits characteristically reduce the patient's VOR time constant to rotation, presumably by altering the bilateral input to a central velocity storage process that normally prolongs the VOR response. This deficit is poorly understood because there has been, until now, no means by which to assess VOR dynamics independently for each ear. In Aim 1, a novel caloric step stimulus will be used to evaluate the VOR dynamics independently from each ear of patients with unilateral and bilateral vestibular disease. Models will be developed and used to explain the results and the deficits. The second problem focuses on the long-standing conundrum of temporal masking, which is represented by elevated hearing thresholds before and after the presentation of an acoustic masker. Some listeners with communication deficits exhibit exaggerated temporal masking. To establish the nature of these deficits, a single unified measurement will be used in Aim 2 to characterize the processes that contribute to the dynamic temporal masking response. Temporal properties of the stimuli will be cued by secondary stimulation to test the hypothesis that these dynamic deficits reflect, in whole or part, a signal/masker discrimination problem rather than a temporal masking deficit per se. Simulations will help delineate peripheral and central auditory contributions to the dynamic deficits. This pair of challenging clinical research problems will offer outstanding mentoring opportunities to involve young clinical investigators directly in a multidisciplinary patient-oriented research program.